1. Field of the Invention
The invention relates to an improved foundation system for anchoring manufactured structures in place to withstand high winds.
2. Background of the Invention
Manufactured structures, especially manufactured housing and mobile homes, have a history of susceptibility to storm damage arising from high winds. A characteristic of these structures is that they are built on longitudinal frame members or stringers beneath the floors. The width and the structures themselves are designed for over the road transport. A typical 14 foot wide unit is built on two longitudinal frame members and two of these are put together to form a 28 foot wide unit on four longitudinal frame members. It is quite important that manufactured housing has the appearance of a site built home. This means, among other things, that the structure must be supported at about grade level. A common installation involves concrete pier footings upon which concrete blocks are placed at the desired height. Shims introduced between the concrete blocks and the bottom of the 10 or 12 inch longitudinal stringers of the structure are used as leveling devices. Tiedown straps about every 6 to 8 feet around the periphery of the structure are connected to "augers" which are screwed into the ground beneath the peripheral walls. Some kind of skirting is employed to hide the foundation. Codes require that the floor be at least 8 inches of above grade so that ground water cannot reach or damage the floor structure. Despite the use of numerous tiedowns at the edges and straps placed at intervals along the length over the roof structure, which can be tied down on either side of the structure, wind damage continues to be a major problem. Open space under manufactured housing can contribute to wind damage by creating a lifting effect in very strong winds.
An improved foundation system for manufactured homes is disclosed in U.S. Pat. No. 4,738,061. Footings set in an excavation in the ground have fixed thereto vertical support members which are attached to the longitudinal frame members of a manufactured building. The structure is supported at about grade level. A rigid system of overlapping fiberglass panels with vertical ribs define a retaining wall for backfilling around the outside perimeter of the structure. Rigidity of the fiberglass panels against being caved in by the backfill is provided by a series of triangular shaped vertical reinforcing ribs spaced at 1-foot intervals along the panel. This makes for a difficult and expensive construction process. These panels are composite structures of fiberglass and wood in which the triangular wood stiffeners are encapsulated between two layers of fiberglass in order to prevent deterioration of the wood caused by the combination of moisture and various organisms. This structure is mechanically complicated and expensive. It is costly to rip the wood, lay it in and work fiberglass around it so it doesn't cut the glass. Consequently this structure consumes more fiberglass resin than would a flat panel. It is difficult to control the amount of materials and uniformity of the structure with a composite of this shape employing wood. It would be desirable to have a simple less expensive structure not difficult to manufacture, for a supporting system of this kind, which securely anchors a manufactured structure at grade level. It would also be desirable to produce a simpler support structure which supports vertical loads and horizontal wind forces using less material which is less expensive than the structure shown in the patent. An improved support structure of this kind which provides solid support at grade level for manufactured housing which is simpler, less costly to make and to install is the subject of the present invention.